الفهرس | Only 14 pages are availabe for public view |
Abstract Abstract Lipid production in terms of oil percentage and fatty acid composition of Nostoc paludosum, Anabaena torulosa and Phormidium ambiguum, which were identified morphologically by light microscope and genetically via 16S rRNA gene sequence amplifications were studied in the control state and in response to 4 different stress factors. Salinity stress ranging from 50 to 250mM NaCl, nitrogen and phosphorus stress regimes (50% NO3- N, 50% PO4-P of BG11 media) and lastly the collective effect of all the 3 stressors combined. The results indicated that there were changes in the physiological behavior under all these different kinds of stress which are also illustrated genetically. Oil extraction by Hexane-isopropanol method was performed for analysis of lipid content. The results revealed that the optimum lipid production for N. paludosum, A. torulosa and P. ambiguum was observed at 250mM NaCl stress, 50% phosphorus and at 100mM NaCl stress, respectively. Gas chromatography mass spectrometry (GC/MS) analysis of fatty acid composition revealed that the main constituent of these fatty acids was classified as suitable for biodiesel due to their long methyl ester chains. These results were explained genetically using RAPD-PCR technique which revealed the appearance and disappearance of some bands. Subsequently, this led to change in DNA sequence which in turn led to DNA polymorphism recording 47.06%, 41.25% and 57.89% for N. paludosum, A. torulosa and P. ambiguum respectively. These 4 treatments generated some genetic mutations which induced changes in the DNA sequence which showed physiologically in the lipid profiles of the 3 species. Nostoc paludosum and P. ambiguum had higher SFAs, while A. torulosa had higher PUFAs values. The DNA banding pattern indicated that stress of nitrogen, phosphorus, salinity and combined stress caused more changes compared to control. Thus, the stress changes that were observed in the physiological studies were confirmed genetically. |